Automatic choke for a carburetor



Dec. 30, 1969 J. L. szwARGuLsKl 3,486,742

AUTOMATIC CHOKE FOR A CARURETOR Filed March 21, 1968 Y |NvENToR JESSE L. SZWARGULSKI BMZ/W' ATTORNEY United States Patent() 3,486,742 AUTOMATIC CHOKE FOR A CARBURETOR Jesse L. Szwargulski, Florissant, Mo.assignor to ACF Industries, Incorporated, New York, N.Y., a corporation of New Jersey Filed Mar. 21, 1968, Ser. No. 715,062 Int. Cl. F02m 1/10 U.S. Cl. 261-39 11 Claims ABSTRACT F THE DISCLOSURE A vacuum or air motor for slowly opening a carburetor choke valve during cold engine starting and allowing unretarded closing of the choke valve has a check valve with a self-cleaning bypasswhich prevents clogging of a restricted orifice thereof. According to an additional feature of the invention the check valve includes a bimetallic plate which causes'the valve to open in resnonse to temperature as well as pressure.

Background of the invention Carburetors commonly have an unbalanced buttery `type choke valve blade `operated by a thermostatic spring.

It hasbeen found desirable to begin opening the choke immediately after the engine starts, and for this purpose a vacuum motor is connected to the choke to open it in response to intake manifold vacuum, as shown in Patents 3,190,623, 3,262,683 and 3,321,194, all of which are in Class 261-39. In order to provide retarded actuation of the air motor in responseto manifold Vacuum, but a rapid movement of the motor in the opposite direction yin response to an increase of manifold pressure, itis proposed in Patent No. 3,190,623 to connect the motor to the manifold through a check valve having a bypass with an extremely small orice. The `orifice diameter is only a few thousandths of an inch and, therefore, is very easily clogged. It is an object of this invention to prevent such clogging.

Another objective of the invention is lto retard the opening of the choke after engine starting only when the yambient temperature is low.

Summary of the invention The carburetor choke valve is connected to thermostatic means which resiliently urgesit closedv when .the -engine is cold. The choke valve is also connected to pressure responsive actuating means for slowly opening the choke valve upon starting of the engine. The -slow opening characteristic of the actuating means results from a check valve in a conduit between the actuating means and a point downstream of the carburetorthrottle valve. 'Ihe check valve has a very restricted bypass for permitting slow operation of the actuating means when the intake manifold pressure drops in response to engine starting. A movable rod is placed in the restricted bypass to loosen and remove contaminants therefrom, and to thereby prevent it from becoming clogged. In order to obtain a rapid opening of the choke valve immediately after engine starting at warm ambient temperatures, say above 70 Fahrenheit, the check valve closing member is a bimetallic disc which pops open when the selected temperature is reached.

Brief description of the drawing The invention will be understood from the following description of the several embodiments thereof and their .illustration in the accompanying drawing, wherein:

FIG. 1 shows a carburetor choke valve actuated by a pressure responsive motor according to the invention.

3,486,742 Patented Dec. 30, 1969 "ice Description of the preferred embodiments Referring to the drawing, the carburetor 10` includes a choke 12 pivoted at 14. A lost motion linkage 16 connects the choke valve 12 to vacuum motor 20 and includes a plunger 17 biased in the choke opening direction by spring 18. Motor 20 includes a diaphragm 22 biased by spring 24 within a housing 26 having a chamber 28 vented to atmosphere, and an air tight chamber V30. The latter is connected to a vacuum source, such as the intake manifold, by a conduit 32. The conduit communicates with chamber 30 through check valve mechanism 34 comprising a perforated wall 36 and annulus 38 xed therein. Between wall 36 and annulus 38 is exible flapper valve 40, which is adapted to move away from wall 36 to uncover openings 42, when the pressure supplied by conduit 32 is greater than that in chamber 30. A small central hole 44 extends through annulus 38 and contains a loosely tting rod or wire 46. Hole 44 provides a restricted passage bypassing check valve 34. The

`choke valve is also connected to thermostat 50 through linkage 52 and a lever 54 fixed on choke valve shaft 14. The arcuate slot 56 of sector arm 58 is long enough to permit full opening of choke valve 12 by thermostatic spring 50.

When a pressure drop occurs in the intake manifold upon starting of the engine, flapper valve 40 remains closed, but chamber 30 is slowly exhausted through bypass 44. Diaphragm 22 then moves against the force of spring 24. Plunger 17 is urged against diaphragm assembly 22 by spring 18 to open choke valve 12 gradually over a period of a number of seconds. Spring 18 tends to open the choke against the force exerted by `thermostat 50 to close the choke. The relationship and operation of diaphragm 22 and plunger 17 and their associated Springs 18 and 24 are substantially the same as the corresponding elements of Patent No. 3,321,194. The present invention, however, permits fast operation of motor 20 in response to an increase of pressure and lslow operation in response to a decrease of pressure inconduit .`32. TheV slow motor action is caused by the very restricted .bypass passage 44. The diameter of passage 44 maybe, for example, 0.013V inch and the diameter of rod 46 may be 0.011 inch. These small sizes andthe considerable relative length of passage 44 cause the slow operation of motor 20, and the retarded opening of choke 12.`Rod 46 will vibrate and move axially in passage 44 due to engine vibration, movement of and impact by diaphragm 22, and air currents, and in so doing will tend to keep passage 44 unclogged by particles which might otherwise collect in restricted passage 44. It is an important feature of wire or rod 46 that it provides a self cleaning action, in addition to restricting the flow through bypass 44- to provide adequate retardation of the operation of motor 20.

FIG. 3 shows a thermal check valve for use in motor 20 of FIG. l, instead of check valve 34. In the embodiment of the invention illustrated in FIG. 3 a portion of motor body 26 is indicated. Within body 26 is a closetting annulus 60 having an inwardly turned ange 61. An arcuate bimetallic disc 62 is urged against plate 63 by spring 64. Disc 66 has several openings 62 outwardly of the region of seat 68 and a very small orice 70 at its center. Plate 63 forms the bottom of cup 72, which is fixed in annulus 60, and has at its center a relatively large opening 74. A bent pin or rod 76 similar to rod 46 of FIG. 2, is placed in openings 70 and 74.

When an increased pressure is applied to the outer side of disc 62, it is urged oif seat 68 against compression spring 64 to open the valve. Air then flows through openings 74 and 66 and around the outer edge of disc 62 into chamber 30 of motor 20. The motor is then actuated rapidly to a position permitting choke valve 12 to remain `partially open. If the manifold pressure drops, or stabilizes, spring 64 urges disc 62 into engagement with seat 68, and the valve is then closed, except for the restricted bypass through orifice 70. Bimetallic disc 62 is designed so that it will pop over into the form indicated by dashed line 78 at a predetermined temperature. When this action occurs, the valve opens. In other words, the valve is a check valve responsive to both temperature and pressure. Pin 76 serves to keep orice 70 clean and unclogged as disc 62 moves back and forth along the pin. Disc 62 may be coated with Teon or a similar plastic material to reduce contaminating deposits thereon of gum, varnish or the like. The valve of FIG. 3, incorporated in the structure of FIG. 1, retards the opening of choke 12 during engine starting only when the ambient temperature is below a given level. Above this temperature, disc 62 pops off its seat and allows substantially free ow through the valve in both directions, and consequently unretarded operation of motor 20.

The check valve structure shown in FIG. 4 is substantially identical to that of FIG. 3. The principal diiference resides in the fact that no biasing spring such as 64 is used. Instead the disc 62 is free to oat to a seated or unseated condition in accordance with the diiferential pressure existing at the time. When pressure in space 30 is greater than in the conduit 32, the disc 62 will seat and restrict ilow. Upon a reversal of pressures, the disc will unseat for rapid ow of air through the opening 74.

I claim:

1. In a carburetor for a gasoline engine having a choke connected to a thermostat for opening and closing the choke, and a vacuum motor connected to the choke, the vacuum motor communicating with the intake manifold through a restricted passage, the improvement comprising means including a member movable in the restricted passage during engine operation for freeing and removing foreign particles from the restricted passage to prevent clogging thereof.

2. The invention according to claim 1, wherein said movable member is a rod mounted in said restricted passage for axial movement therethrough.

3. The invention according to claim 2, wherein said rod has a cross-sectional area equal to more than half the area of the restricted passage.

4. The invention according to claim 3, wherein said vacuum motor has a movable diaphragm positioned to engage said rod for moving said rod,

5. The invention according to claim 3, wherein said rod extends through said passage and beyond the ends thereof and includes stops at its outer ends for holding the rod loosely captive in said passage.

6. The invention according to claim 1, including a conduit having a check valve connecting said vacuum motor to the intake manifold, said restricted passage forming a bypass for said check valve.

7. The invention according to claim 6, wherein said check valve includes a seat having an opening therein, and a valve element having a movable portion adapted to seal against said seat for closing the opening in said seat, said restricted passage extending through said valve element.

8. The invention according to claim 6, wherein said check valve includes thermally responsive means for Opening it at a desired temperature.

9. The invention according to claim 8, wherein said check valve includes a seat and said thermally responsive means includes a bimetallic disc postioned to engage the seat at given temperatures and adapted to ex away from said seat to open the check valve at desired higher temperaturcs.

10. The invention according to claim 6, wherein said check valve is spring biased to its closed position and includes means for opening it in response to a predetermined temperature or a rise in intake manifold pressure.

11. A carburetor for a gasoline engine, comprising a choke; connected to a thermostat for opening and closing the choke; a pressure responsive actuator, and a lost motion connection between the actuator and the choke for opening the choke and for enabling the thermostat to open and close the choke; a conduit connecting the actuator to the intake manifold of the engine; a check valve in said actuator, having a valve seat and valve means for engaging said seat to close the valve; said valve means including a temperature responsive bimetallic plate adapted to move away from said seat to open the valve upon a rise in temperature, said plate having a relatively small opening for partially bypassing said valve when it is closed.

References Cited UNITED STATES PATENTS 2,942,596 6/1960 Carlson 261-39 2,969,783 1/1961 Braun 261-39 2,979,047 4/ 1961 Rapplean et al. 261-39 3,190,623 `6/1965 Ball 261-39 3,294,375 12/ 1966 Szwargulski 2,61-39 X 3,313,531 4/1967 Winkley et al. 261-39 X TIM R. MILES, Primary Examiner 

